Nootka is available for Windows, Linux, macOS, Android operating systems. http://nootka.sourceforge.net/
"Learn an instrument with this open source music teacher" (Article Source: Opensource.com) https://opensource.com/life/16/7/introducing-nootka
"How to make a low-cost guitar amp with Linux" (Instruction Source: Opensource.com) https://opensource.com/article/17/8/linux-guitar-amp
With just a guitar, a cable, and open source software, you've no need to "Gimmie Some Money" to take your home recording studio to 11.
"MOD Duo: Building an open source guitar stomp box" (Instruction Source: Opensource.com) https://opensource.com/life/16/10/mod-duo-multiple-guitar-stomp-boxes-single-device
It runs Linux, uses JACK, and the plugin standard used is LV2.
"How to build an open hardware guitar amplifier in 5 steps" (Instruction Source: Opensource.com) https://opensource.com/life/16/1/build-open-hardware-guitar-amp